1. Field of the Invention
The present invention relates to a display apparatus and a control method thereof, and in particular, to a display apparatus with an adjustable backlight unit and a control method thereof. The present application is based on Korean Patent Application No. 2002-40098, filed Jul. 10, 2002, which is incorporated herein by reference.
2. Description of the Related Art
Since a Liquid Crystal Display (LCD) employs a non-light emitting element, different from a Plasma Display Panel (PDP), a Field Emission Display (FED), etc., it is not possible to use it where light does not exist.
In order to compensate for this defect of the LCD, a backlight unit is developed for illuminating light homogeneously on its information display screen.
FIG. 1 is a block diagram of a conventional Thin Film Transistor (TFT)-LCD with the backlight unit. The TFT-LCD includes an image signal processing unit 10, a chromatic signal output unit 20, a Low Voltage Differential Signaling (LVDS) 30, a TFT-LCD panel 40, an inverter 50, and a controller 60.
The image signal processing unit 10 performs signal processing to satisfy a TFT-LCD characteristic for input image signals.
The chromatic signal output unit 20 outputs an RGB signal to satisfy a characteristic of the TFT-LCD panel 40 from the processed image signals.
The LVDS 30 transmits digital Red (R), Green (G), Blue (B) signals to the TFT-LCD panel 40.
The TFT-LCD panel 40 comprises a LVDS and timing processing unit 41 for processing chromatic signals transferred from the LVDS 30 and controlling timing with the chromatic signals, a DC/DC converter 42 for raising voltages to be provided to a gate driver 46 of the TFT-LCD module 48, which generally requests a high voltage driving power source, a V-com generator 43 for providing voltages to common electrodes of each transistor of the TFT-LCD module 48, a gamma correction unit 44 for controlling brightness and color coordinates, etc., in order to correct a difference between the display characteristic of the TFT-LCD and the human visual perception characteristic for the gray scale of the image signals, a source driver 45 for transferring voltages of gray scale according to image data to source electrodes of each transistor (not shown) which consists each pixel of the TFT-LCD module 48, a gate driver 46 for driving gates of the transistors consisting each pixel of the TFT-LCD module 48, the TFT-LCD module 48 for displaying images by means of transistors activated by signals transferred through the gate driver 46, and a backlight unit 47 for illuminating the light on the image display screen of the TFT-LCD module 48.
The inverter 50 provides driving currents to the backlight unit 47 of the TFT-LCD panel in response to a control signal output from the controller 60.
The controller 60 controls an overall display apparatus in order to enable the transferred image signals to be displayed on the image display screen through the TFT-LCD module 48, and in particular, controls the inverter 50 in order to drive the backlight unit 47 illuminating the light on the image display screen of the TFT-LCD module 48.
As described above, in the conventional TFT-LCD, the backlight unit 47 illuminates the light on the image display screen using currents provided through the inverter 50, and a user can see the image via the image display screen due to the illuminated light.
However, since the currents are designed to be provided constantly to the backlight unit 47 via the inverter 50 in the conventional TFT-LCD, the light is only to be constantly illuminated on the TFT-LCD module in a predetermined amount. Consequently, there occur problems in that the brightness of the input image signals is not controlled efficiently. That is, relatively better quality of the display can be provided by providing more currents to the backlight unit to raise the brightness when the amount of reproduced signals in the LCD is small and limiting maximum currents provided to the backlight unit when the amount of reproduced signals in the LCD is large. However, since the currents provided to the backlight unit through the inverter remain constant, the quality of the display image can be deteriorated.